My Google Map Blog

On March 30th, 2017, a fire started under an overpass along the I-85, one of the major routes through Atlanta, Georgia, USA. The fire resulted in a section of the overpass collapsing and major repairs being needed to other sections of the roadway. Google Earth now features an image dated April 1st, just two days after the event. Already we can see work being done to repair the road. According to Wikipedia, repairs were completed by May 13, just six weeks after the collapse.

Collapsed bridge in Atlanta, Georgia.

Almost before the fire was out, people were checking Street View to see what had been under the bridge that could have caused such a major fire. Apparently there were some plastic conduits that had been stored under the bridge:

Conduits stored under the bridge as seen in Street View in March 2017 (the month of the fire)

Using the Google Maps version of Street View, we can go through the historical imagery, which allows us to see that the material was placed there some time between July 2011, and April 2012.

No materials in July 2011.

Materials stored under the bridge by April 2012.

Although in this case, the local government had records of what had been stored there, this sort of event highlights how useful both overhead imagery and Street View can be for quickly and easily checking the recent history of a location. We get quite a lot of emails asking whether we can obtain more imagery than is in Google Earth or Street View to help settle a dispute or identify when some event occurred. Unfortunately, we cannot help in such cases as we do not have access to any imagery not already available on those platforms and Google does not supply imagery for such purposes via other channels either.

There are, however a few things to keep in mind with regards to what is a relatively new public ‘historical record’ of the world:

• How frequently imagery is updated and the resolution of imagery varies significantly from place to place. In many cases, even when Street View or overhead imagery would be suitable for what you want to find out, it simply isn’t available for the dates you are interested in.
• It is not live and there may be a period of months or years between the time imagery is captured and when it is published. It will typically not help you track down a stolen vehicle or find a lost person.
• Be careful with dates. Do not be too trusting of the dates on aerial imagery, especially when it is sourced from third parties. Older aerial imagery in particular is often incorrectly dated. Satellite imagery dates are typically much more reliable. Street View is only dated to the month and we do not know how accurate the dates are.
• A significant proportion of the world doesn’t yet have Street View, and only some areas have high resolution aerial imagery (mostly the continental US, parts of Europe, Japan and New Zealand). Satellite imagery is often only useful for large scale phenomena.

It would be great if Google were to increase the accuracy of the dates on the imagery. The satellite imagery suppliers do know the exact time that each image was captured and it would be fairly easy for Google to have timestamps on the photos used for Street View. So why don’t they? It is possible they are concerned about the privacy implications of time stamps on Street View. They may also be concerned about the possibility of making mistakes. If Google gives an exact timestamp then the expectation that it is accurate is much higher.

The post Google Earth and Street View as an historical record appeared first on Google Earth Blog.

We recently came across a story about the world’s largest floating solar power plant to date being turned on in China. Despite the article being repeated by many news agencies we found it very difficult to figure out the exact location of the solar plant. Eventually we found this drone footage showing the power plant and we were able to positively identify the location in Google Earth. A few solar panels from the plant were captured at the edge of an image from November, 2016. Strangely enough, we then found this drone footage claiming to be of the same solar plant, but it is clearly a different location. We managed to identify its location too. It is a bit older and can be clearly seen in a November, 2016 image:

Floating solar power plant in the same region as the new record holder.

Nearby, we found a solar plant under construction that looks like it will be partially over the water but anchored to the ground rather than floating.

Solar plant under construction. There are also arrays of stakes off the edge of the above image, so it will be quite a large solar plant.

There were many coal mines in the region and the area has suffered subsidence as a result of the mining, which created new lakes. The new record-holding floating solar plant is on one of those lakes, so it serves as a symbol of transformation from coal to renewables.

This village was partially flooded due to subsidence. It appears that houses remaining on dry land were demolished.

Another village flooded as a result of subsidence.

We also found a lot of other solar plants in the region built over water, such as this one along a river:

Putting solar panels over water has a number of advantages vs dry land:

• Solar panels become less efficient as they heat up. The water helps to cool the panels, which increases their efficiency.
• When used on reservoirs, they reduce evaporation, saving valuable water.
• In regions where land is in short supply, such as Japan, it avoids wasting valuable space.

Almost all the solar plants we found had the panels aligned east to west, tilted towards the south, to catch the most sun. But one interesting idea we came across was an experimental floating solar plant in South Korea that rotates, significantly increasing efficiency:

Speed in milliseconds per image:
Rotating solar power plant in South Korea. See on YouTube

It is presumably cheaper to rotate a whole floating solar plant than land based systems that rotate individual panels to track the sun. The rotation observable in the Google Earth imagery is not very much, but that is likely a consequence of the fact that most imaging satellites have orbits arranged so that they take pictures around mid-day, so we do not see the early morning and late afternoon positions.

We came across this article discussing the advantages of floating solar panels, and it mentions that solar plants built over water are often combined with fisheries. It also mentions that the Anhui region of China, where the first solar plants we looked at above are situated, is expected to get around 3.2 GW of floating solar between 2016-2018, so the world record 40 MW plant is just a small part of a much bigger scheme.

For some pictures of floating solar around the world see this website.

For the locations of the places mentioned above as well as many other floating solar plants in China, Japan, and the United Kingdom, download this KML file. We have also included a few dry land solar plants that we found nearby while looking for floating plants, and a few major solar plants in China.

The post Floating Solar Plants appeared first on Google Earth Blog.